Prehistoric Armored Mammal Found in Chile
for National Geographic News
|December 12, 2007|
Fossils found in South America's Andes mountains belong to a new species of the ancient armored mammals called glyptodonts, scientists say.
Relatives of the modern armadillo, glyptodonts were clumsy, bizarre-looking mammals covered with thick, immovable plates.
The animals—which perished at the end of the Ice Age several thousand years ago—could grow to the size of a small car.
The newfound fossils are from the Miocene epoch (about 5 to 23 million years ago) and offer important insights into the evolution of the strange creatures, paleontologists say.
But scientists who study fossils to reconstruct ancient ecosystems say the fossil also helps reveal surprising aspects of South America's ancient geography.
U.S. and Chilean scientists found the specimen three years ago while working near a site known as Salar de Surire in northern Chile. The location is some 14,000 feet (4,267 meters) above sea level.
"We had worked at the site several times and had a good idea of the sort of animals that were there," said Darin Croft, a mammalian paleontologist from Case Western Reserve University in Ohio. "But we hadn't found a good glyptodont fossil."
But in 2004, when Croft and his colleagues returned to Salar de Surire, "we were casually looking around and happened to see osteoderms [plates of bones that form the new glyptodont's shell] eroding out of the ground," he said.
Three days of digging revealed parts of a shell, a jaw, and a limb bone.
"We didn't immediately recognize it as new," Croft told National Geographic News.
"It wasn't until we brought the specimen back and cleaned the bones did we realize it wasn't quite like anything else around."
The new species—which Croft and his team named Parapropalaehoplophorus septentrionalis—was a relatively small glyptodont, Croft said, weighing about 200 pounds (91 kilograms).
Because the fossil is only known from one location, the team isn't sure why the species went extinct, he added. But he pointed out that the new fossil contained partial hinges in its armor.
"Nearly all later glyptodonts have lost their hinges, while early glyptodonts still retained parts of a hinge or couple of hinges," he said.
"Ours has a solid shell, but these partial hinges told us we had a primitive glyptodont closer to what ancestral glyptodonts looked like."
This animal probably died off long before the last glyptodont went extinct, around the time humans came to the New World, he said. (Related: "Humans Caused Australia's Ice Age Extinctions, Tooth Study Says" [January 24, 2007].)
The study, led by Croft, appears in the latest Journal of Vertebrate Paleontology.
"This represents the oldest glyptodont known from any significant skeletal remains," said Timothy Gaudin, a biologist at the University of Tennessee who was not involved with the study.
"Other early glyptodonts are known only from scraps of skeletons. It will help us understand how glyptodonts evolved from their presumably more armadillo-like ancestors."
The location of the fossil at an unexpectedly high altitude is important to scientists studying the biodiversity of ancient South America—how animal populations where dispersed and how those patterns changed over time—Gaudin added.
Clumsy and large, glyptodonts likely lived on flat plains. Indeed, most fossils have been found in low elevation sites.
"Was the animal living at 14,000 feet? Probably not," said Greg McDonald, a U.S. National Park Service paleontologist. "It probably lived much lower.
"For me, the real question is what this tells us about the history of uplift of the Andes mountains and how it impacted this group of animals."
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